Carbon composite material and dispersion liquid

Abstract

Provided are: a carbon composite material which has good heat resistance, has good dispersibility when made into a dispersion liquid, and is unlikely to re-aggregate; and a dispersion liquid in which the carbon composite material is dispersed. A carbon composite material obtained by introducing a modifying group into a carbon material, the carbon composite material having a particle diameter (D50) of 0.5-15.0 [mu] m at a cumulative 50% from the small particle side in a volume-based particle size cumulative distribution as measured by laser diffraction scattering, the proportion of particles having a particle diameter of 50.0 [mu] m or more being 30.0 vol% or less, and the particle diameter (D50) of 0.5-15.0 [mu] m being the cumulative 50% from the small particle side. The cation modification rate of the carbon composite material calculated by formula (1) is 1.0-50.0, and the modification group contains an anionic functional group and a counter cation of the anionic functional group. Cationic modification rate (mass ppm / (m2 / g) = cation concentration (mass ppm) / specific surface area (m2 / g) (1)

Description

Technical Field

[0001] The present invention relates to a carbon composite material and a dispersion liquid obtained by dispersing the carbon composite material. Background Art

[0002] Carbon materials are materials that have attracted much attention. For example, graphene is a substance containing a two-dimensional crystal composed of carbon atoms and has excellent electrical, thermal, optical, and mechanical properties. Graphene is expected to be widely used in fields such as graphene-based composite materials, nanoelectronics, flexible / transparent electronics, nanocomposites, supercapacitors, batteries, hydrogen storage, nano medicine, and bioengineering materials.

[0003] In order for graphene to exhibit the above effects, graphite needs to be exfoliated into a graphene state. However, even if graphite is once exfoliated into a graphene state, re-aggregation sometimes occurs.

[0004] As a method for preventing the re-aggregation of graphene, a method of intercalating an alkali metal between the layers of graphene and coating the surface of the graphene with an organic halogen compound is known (see Patent Document 1). In addition, as another method, a method of introducing an oxygen-containing group onto the surface of a carbon material to form graphene oxide is known (see Patent Document 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-19695.

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2013-212948. Summary of the Invention

[0009] The present invention provides the following.

[0010] [1] A carbon composite material, which is a carbon composite material obtained by introducing a modifying group into a carbon material. In the volume-based particle size cumulative distribution measured by the laser diffraction scattering method, the cumulative 50% particle size (D50) starting from the small particle side is 0.5 to 15.0 μm, the occupancy ratio of particles having a particle size of 50.0 μm or more is 30.0% by volume or less, and the cation modification rate of the carbon composite material calculated by the following formula (1) is 1.0 to 50.0. The modifying group contains an anionic functional group and a counter cation of the anionic functional group.

[0011] Cation modification rate (mass ppm / (m 2 / g)) = cation concentration (mass ppm) / specific surface area (m 2 / g) (1)

[0012] [2] For the carbon composite material described in [1] above, wherein,

[0013] The anionic functional group includes at least one or more selected from the group consisting of carboxyl group, carbonate group, sulfonic acid group, and phosphoric acid group.

[0014] [3] For the carbon composite material described in [1] or [2] above, wherein,

[0015] The counter cation includes at least one or more selected from the group consisting of potassium ion, sodium ion, lithium ion, barium ion, calcium ion, magnesium ion, rubidium ion, and ammonium ion.

[0016] [4] For the carbon composite material described in any one of [1] to [3] above, wherein,

[0017] The concentration of the counter cation contained in the carbon composite material is 50 to 5000 mass ppm.

[0018] [5] For the carbon composite material described in any one of [1] to [4] above, wherein,

[0019] The oxygen content rate contained in the carbon composite material is 0.01 to 2.00 mass%.

[0020] [6] For the carbon composite material described in any one of [1] to [5] above, wherein,

[0021] The carbon material of the base material of the carbon composite material includes at least one or more selected from the group consisting of graphite, natural graphite, artificial graphite, flake graphite, expanded graphite, pyrolytic graphite, graphene, and carbon nanotubes.

[0022] [7] A dispersion liquid, wherein,

[0023] The dispersion liquid is a dispersion liquid in which the carbon composite material described in any one of [1] to [6] above is dispersed in a dispersion medium. Detailed implementation mode

[0024] Hereinafter, the present invention will be described in detail with reference to an implementation mode.

[0025] In this specification, the description of "XX to YY" means "XX or more and YY or less". In addition, in this specification, for a numerical range (for example, a range of content, etc.), the lower limit value and the upper limit value described in stages can be combined independently of each other. In addition, in the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range can also be replaced with the value shown in the examples.

[0026] In this specification, "graphene" refers to "a sheet-like material containing sp2-bonded carbon atoms with less than 50 layers".

[0027] In the method described in Patent Document 1, graphene has the effect of preventing aggregation by making an organic halogen compound act as a steric hindrance. However, since the organic halogen compound becomes an impurity, graphene cannot fully achieve the above effect and its uses are limited. In addition, in the method described in Patent Document 2, although the dispersibility of graphene oxide is improved, the surface of graphene is oxidized, resulting in an increase in structural defects and the inability to fully achieve the above effects of graphene. Further, graphene oxide such as that in Patent Document 2 contains oxygen, and thus, for example, when exposed to high temperatures during the manufacturing process, it is sometimes prone to thermal decomposition and disappearance.

[0028] The present invention can provide a carbon composite material and a dispersion liquid obtained by dispersing the carbon composite material, the carbon composite material having good heat resistance, good dispersibility when made into a dispersion liquid, and being difficult to re-aggregate.

[0029] [Carbon composite material]

[0030] The carbon composite material of the present invention is a carbon composite material in which a modifying group is introduced into a carbon material. In the volume-based particle size cumulative distribution measured by laser diffraction scattering method, the cumulative 50% particle size (D50) starting from the small particle side is 0.5 to 15.0 μm, the occupancy ratio of particles with a particle size of 50.0 μm or more is 30.0 volume% or less, and the cation modification rate of the carbon composite material calculated by the following formula (1) is 1.0 to 50.0. The modifying group contains an anionic functional group and a counter cation of the anionic functional group.

[0031] Cation modification rate (mass ppm / (m 2 / g)) = cation concentration (mass ppm) / specific surface area (m 2 / g) (1)

[0032] (Carbon material)

[0033] The carbon composite material of the present invention is obtained by introducing a modifying group into a carbon material as a base material.

[0034] The carbon material is not particularly limited. Examples of the carbon material include graphite, natural graphite, artificial graphite, flake graphite, expanded graphite, pyrolytic graphite, graphene, and carbon nanotubes. From the viewpoint of dispersibility, the carbon material can be graphene or graphite that becomes graphene in the dispersion liquid.

[0035] As a mode, the carbon material as the base material of the carbon composite material may include at least one or more selected from the group consisting of graphite, natural graphite, artificial graphite, flaky graphite, expanded graphite, pyrolytic graphite, graphene, and carbon nanotubes.

[0036] The average particle diameter of the carbon material is not particularly limited. As a mode, from the viewpoint of dispersibility, it may be 1 to 700 μm, may be 3 to 500 μm, may be 5 to 300 μm, or may be 10 to 200 μm.

[0037] As another mode, from the viewpoint of increasing the fracture surface of the carbon material and more imparting modifying groups, the average particle diameter of the carbon material may be 50 to 700 μm, may be 200 to 700 μm, may be 300 to 700 μm, or may be 350 to 700 μm.

[0038] In the present invention, the average particle diameter of the carbon material refers to the particle diameter (D50) at which the cumulative number is 50% in the particle size distribution. The average particle diameter of the carbon material can be measured by using a laser diffraction type particle size distribution meter (for example, MT3300EXII, manufactured by MicrotracBEL Co., Ltd., Japan).

[0039] Graphene is a flaky substance having a hexagonal lattice structure in which carbon atoms are bonded. Graphene may be in a single-layer state having a layer thickness of one carbon atom, may be in a multi-layer state of 2 or more layers and less than 50 layers, may be in a multi-layer state of less than 20 layers, or may be in a multi-layer state of less than 10 layers.

[0040] As the content of carbon atoms in graphene, there is no particular limitation, and it may be 95% by mass or more, may be 99% by mass or more, or may be 100% by mass.

[0041] As the content of impurities in graphene, there is no particular limitation, and it may be 5% by mass or less, may be 1% by mass or less, or may be 0% by mass.

[0042] From the viewpoint of dispersibility, the thickness of graphene may be 0.3 to 35.0 nm, may be 0.3 to 12.0 nm, or may be 0.5 to 7.0 nm.

[0043] The "thickness" mentioned here refers to the thickness of one layer in the case of a single layer and the thickness of the entire layer in the case of a multi-layer.

[0044] For the thickness of graphene, for example, an atomic force microscope can be used for measurement.

[0045] (Modifying group)

[0046] The modifying groups possessed by the carbon composite material are not particularly limited. From the viewpoint of making it difficult for the carbon composite material to re-aggregate, the modifying groups possessed by the carbon composite material are groups composed of an anionic functional group and a counter cation of the anionic functional group.

[0047] It is speculated that the anionic functional group of the above-mentioned modifying group binds to the carbon material, and counter cations are attracted around the negatively charged carbon material.

[0048] The modifying group is composed of an anionic functional group and a counter cation of the anionic functional group. The carbon composite material having the modifying group dissociates the counter cation in a solvent, thereby generating an electrostatic repulsive force in the carbon material combined with the anionic functional group. Therefore, the carbon composite material of the present invention is easily dispersed in a solvent. Therefore, the carbon composite material of the present invention has good dispersibility when dispersed in a solvent and is difficult to re-aggregate.

[0049] A more detailed description of the above situation is given.

[0050] The carbon composite material of the present invention has the characteristic of being highly negatively charged in a dispersion liquid by binding an anionic modifying group to the carbon material. If the negative charge amount increases, the dispersion index described later becomes higher. However, since general graphene (for example, commercially available: graphene nanoplate (manufactured by XG sciense company, trade name: R10), the negative charge amount of only the pulverized product of graphite is small and the van der Waals force is dominant, the dispersion index is reduced by aggregation. It is considered that the counter anion of the water-soluble salt described later binds to the carbon material through a weak acid dissociation reaction composed of a free radical and a weak acid occurring on the fracture surface of the carbon material. The binding can be any one of a covalent bond, an ionic bond, or a coordination bond, or it can be a situation where the components of the water-soluble salt are physically adsorbed on the carbon material instead of such a binding.

[0051] In addition, the dispersibility of the carbon composite material depends on the amount of attachment of the anionic modifying group to the surface area.

[0052] By setting the particle size to a certain specified value or less, the modifying groups at the particle ends increase, the electrostatic repulsion increases, and the dispersibility is improved. The reaction between a free radical and a weak acid salt (for example, tripotassium citrate) occurring on the fracture surface of the carbon material is promoted by the mechanical energy during pulverization for binding.

[0053] The carbon composite material is formed by binding an anionic modifying group to the fracture surface during the pulverization of the carbon material. Therefore, by setting the particle size to a certain specified value or less, the number of anionic modifying groups is increased. In other words, by promoting pulverization and reducing the particle size, a large number of modifying groups are bound, and the dispersibility is improved.

[0054] From the viewpoint of the dissociability of the counter cation of the anionic functional group, the anionic functional group constituting the modifying group may be at least one selected from the group consisting of a carboxyl group, a carbonate group, a sulfonic acid group, and a phosphoric acid group, or may be a carboxyl group or a carbonate group.

[0055] Alternatively, as another mode, from the viewpoint of the dissociability of the counter cation of the anionic functional group, the anionic functional group constituting the modifying group may include at least one or more selected from the group consisting of a carboxyl group, a carbonate group, a sulfonic acid group, and a phosphoric acid group, or may be a carboxyl group or a carbonate group.

[0056] From the viewpoint of the ionization tendency, the counter cation constituting the modifying group may be at least one selected from the group consisting of a potassium ion, a sodium ion, a lithium ion, a barium ion, a calcium ion, a magnesium ion, a rubidium ion, and an ammonium ion, or may be a potassium ion, a lithium ion, or a sodium ion.

[0057] Alternatively, as another mode, from the viewpoint of the ionization tendency, the counter cation constituting the modifying group may include at least one or more selected from the group consisting of a potassium ion, a sodium ion, a lithium ion, a barium ion, a calcium ion, a magnesium ion, a rubidium ion, and an ammonium ion, or may be a potassium ion, a lithium ion, or a sodium ion.

[0058] When the modifying group included in the carbon composite material is composed of an anionic functional group and the counter cation of the anionic functional group, the concentration of the counter cation contained in the carbon composite material of the present invention may be 50 to 15,000 mass ppm, may be 50 to 13,000 mass ppm, may be 50 to 10,000 mass ppm, may be 50 to 5,000 mass ppm, or may be 100 to 5,000 mass ppm. If the concentration of the counter cation is 50 mass ppm or more, the dispersibility in the solvent of the carbon composite material can be further improved, and if it is 15,000 mass ppm or less, since the electrostatic repulsive force acting on the carbon material to which the anionic functional group is bonded in the solvent becomes stronger, the carbon composite material of the present invention can more easily maintain a dispersed state in the solvent.

[0059] The concentration of the counter cation contained in the carbon composite material can be measured by ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Specifically, it can be measured by the method described in the examples.

[0060] (Particle size of carbon composite material)

[0061] In the volume-based particle size cumulative distribution measured by the laser diffraction scattering method, the cumulative 50% particle size (D50) of the carbon composite material starting from the small particle side is 0.5 to 15.0 μm, and the occupancy ratio of particles with a particle size of 50.0 μm or more is 30.0% by volume or less.

[0062] If the particle size D50 is 0.5 μm or more, it is easy to maintain the crystallinity of the carbon composite material and the dispersibility is improved. If the particle size (D50) is 15.0 μm or less, the crystallinity of the carbon composite material is maintained and the dispersibility is further improved. The particle size (D50) can be 1.0 to 10.0 μm, or can be 1.5 to 5.0 μm.

[0063] If the occupancy ratio of particles with a particle size of 50.0 μm or more is 30% by volume or less, the large particles are reduced and it is easy to peel off, making it easy to improve the dispersibility. The occupancy ratio of particles with a particle size of 50.0 μm or more can be 25.0% by volume or less, or can be 20.0% by volume or less, or can be 5.0% by volume or less.

[0064] In the present invention, the particle size (D50) and particle size of the carbon composite material can be measured by using a laser diffraction type particle size distribution meter (for example, MT3300EXII, manufactured by MicrotracBEL Co., Ltd., Japan).

[0065] The method for controlling the particle size (D50) of the carbon composite material is not particularly limited, and a known pulverization device can be used. For example, dry pulverization devices such as ball mills, planetary mills, stirring mills, bead mills, jet mills, hammer mills, and high-speed stirrers can be cited, and it can also be a ball mill, planetary mill, stirring mill, and bead mill using a medium. From the viewpoint of improving productivity, the rotation speed of stirring can be high and the stirring time can be short. For example, the rotation speed can be 100 to 1000 (rpm), or can be 200 to 800 (rpm). In addition, the stirring time can be 5 to 120 (minutes), or can be 10 to 80 (minutes).

[0066] The average particle size of the carbon material as the base material is as described above. Other processing conditions, etc. can be appropriately adjusted as needed.

[0067] The environmental conditions during pulverization are not particularly limited, and it can be carried out under normal temperature (25 °C) conditions, or in air, or in a nitrogen environment or an inert gas environment such as argon. In addition, as needed, it can be carried out under high temperature or low temperature conditions, or in a pressurized environment or a reduced pressure environment.

[0068] The method for controlling the proportion of particles with a particle size of 50.0 μm or more is not particularly limited. It is sufficient to use a small amount of carbon material, have a long stirring time, and appropriately adjust the rotational speed of stirring. For example, the stirring time can be 5 to 150 (minutes), or it can be 10 to 150 (minutes). The rotational speed can be 150 to 1000 (rpm), or it can be 250 to 800 (rpm).

[0069] It is also possible to use a sieve or the like to sieve out particles of 50 μm or more for adjustment.

[0070] The aspect ratio of the particles of the carbon composite material is not particularly limited and can be appropriately adjusted according to the use. For example, when the carbon material of the carbon composite material is graphite, from the viewpoint of conductivity, the aspect ratio of graphite may be 1 or more, and may also be 10000 or less, or may be 5000 or less, or may be 3000 or less. It should be noted that the aspect ratio of graphite is calculated using the ratio of the size in the planar direction to the thickness. From the viewpoint of dispersibility, the thickness of graphite may be 3.0 nm or more, and may also be 650.0 nm or less, or may be 300.0 nm or less, or may be 100.0 nm or less.

[0071] The thickness of graphite can be measured by an atomic force microscope (for example, manufactured by Hitachi High-Technologies Corporation, model: AFM5300E).

[0072] (Cation modification rate)

[0073] The cation modification rate of the carbon composite material calculated by the following formula (1) is 1.0 to 50.0.

[0074] Cation modification rate (mass ppm / (m 2 / g)) = Cation concentration (mass ppm) / Specific surface area (m 2 / g) (1)

[0075] The cation modification rate is defined as the above cation concentration per unit specific surface area.

[0076] If the cation modification rate is 1.0 or more, the modification groups increase, it is easy to exfoliate, and the dispersibility is improved. Although the upper limit of the cation modification rate is not particularly specified, if it is 50.0 or less, sufficient dispersibility can be obtained. The cation modification rate can be 2.0 to 42.0, or it can be 4.0 to 35.0, or it can be 6.0 to 30.0.

[0077] By appropriately adjusting the processing conditions such as the average particle size of the carbon material, the crushing device, the rotational speed, the stirring time, the medium material, and the medium filling amount, the input amount of the water-soluble salt, the input amount of the raw material carbon material, etc., the cation modification rate can be set within the above range.

[0078] Specifically, the cation modification rate can be measured by the method described in the examples.

[0079] The specific surface area of the carbon composite material of the present invention can be 25 - 130 m 2 / g, or can be 40 - 120 m 2 / g, or can be 60 - 90 m 2 / g. If the above specific surface area is 25 m 2 / g or more, the cation modification rate can be increased. If it is 130 m 2 / g or less, the crystallinity of the carbon composite material can be maintained, the dispersibility in the dispersion can be improved, the ζ potential can be increased, and the dispersion stability can be improved.

[0080] The above specific surface area can be measured by the flowing nitrogen adsorption single point method of JIS R 1626 - 1996. Specifically, it can be measured by the method described in the examples.

[0081] The oxygen content rate of the carbon composite material of the present invention can be 0.01 - 2.00% by mass, or can be 0.10 - 1.50% by mass, or can be 0.20 - 1.00% by mass. If the above oxygen content rate is 0.01% or more, since the anionic functional groups increase and the counter cations increase, the cation modification rate can be increased. In addition, if it is 2.00% by mass or less, since the flame retardancy is easily maintained, the weight reduction is suppressed, and the heat resistance is easily maintained.

[0082] The above oxygen content rate can be measured by, for example, an electron microprobe analyzer (model: JXA - 8539F manufactured by JEOL Ltd.) etc. Specifically, it can be measured by the method described in the examples.

[0083] (Manufacturing method of carbon composite material)

[0084] As a manufacturing method of the carbon composite material of the present invention, for example, a method of adding a water - soluble salt to a carbon material for dry mixing and washing the obtained mixture with water can be cited.

[0085] By causing the anions liberated from the water - soluble salt to combine with the carbon material and be incorporated into the carbon material, the peeling and pulverization of the carbon material are promoted. It should be noted that in the present invention, "pulverization" is not limited to crushing and pulverization that reduce the size compared to the carbon material used as the raw material, but also includes the purpose of simply eliminating the aggregation of the carbon material.

[0086] The carbon material can be the carbon material described above.

[0087] The water-soluble salt is not particularly limited as long as it shows solubility in water. Specific examples of the water-soluble salt include tripotassium citrate, potassium tartrate, potassium acetate, potassium glutamate, potassium carbonate, and tripotassium phosphate. In addition, salts in which potassium of these water-soluble salts is respectively changed to sodium, lithium, barium, calcium, magnesium, rubidium, and ammonium can be cited. One kind of water-soluble salt can be used, or two or more kinds can be used in combination.

[0088] The compounding amount of the water-soluble salt can be 1 to 500 parts by mass, 10 to 400 parts by mass, or 100 to 300 parts by mass with respect to 100 parts by mass of the carbon material. If the compounding amount of the water-soluble salt is 1 part by mass or more, the dispersibility in the solvent is improved due to the formation of the carbon composite material, and if it is 500 parts by mass or less, the reaction and adsorption of the excessive water-soluble salt can be reduced.

[0089] The environmental conditions for mixing and pulverizing the water-soluble salt and the carbon material are not particularly limited. It can be carried out under normal temperature (25°C) conditions similar to those for pulverization as described above, in the air, in a nitrogen environment, or in an inert gas environment such as argon. In addition, if necessary, it can be carried out under high temperature or low temperature conditions, or in a pressurized environment or a decompressed environment.

[0090] Regarding the pulverizing device and its examples, as described above, known devices can be used without limitation. For example, dry pulverizing devices such as ball mills, bead mills, jet mills, hammer mills, and high-speed mixers can be cited. The processing conditions, etc. can be appropriately adjusted according to the type and particle size of the carbon material, etc.

[0091] After mixing the water-soluble salt and the carbon material, the resulting mixture is washed with water. Thereby, the remaining water-soluble salt is removed.

[0092] The amount of water added during washing is not particularly limited as long as it is an amount sufficient to obtain a suspension. If necessary, it can also be heated. For example, water with a mass 10 to 10,000 times the total mass of the water-soluble salt and the carbon material is added and mixed and stirred. For the number of washing times, for example, it can be 2 to 10 times, or 2 to 8 times. The washing conditions can be appropriately set according to the type of carbon material and water-soluble salt used, etc.

[0093] After washing with water, a filter can be used during filtration. For the filter, the most suitable pore size is selected according to the use of the obtained carbon composite material. The obtained carbon composite material can be dried and taken out as a powder, and can also be dispersed in a liquid or used as a paste. Any method can be used for drying. For example, the carbon composite material can be dried by a spray drying method.

[0094] (Dispersion index)

[0095] For the carbon composite material, the dispersion index calculated by the following formula (2) can also be 20 to 70%.

[0096] Dispersion index (X) [%] = [(absorbance) / (absorptivity × cell thickness) / (initial concentration)] × 100 (2)

[0097] (However, in the formula, the absorptivity is 3200 (L / g·m), the cell thickness is 0.0001 (m), and the initial concentration is the concentration of the solid component when dispersing the carbon composite material in a mixed solvent with a volume ratio of water to 2-propanol (IPA) of water:IPA = 6:4, and is set to 3 (g / L).)

[0098] If the above dispersion index is 18% or more, the dispersion of the carbon composite material is good. If it is 70% or less, the interparticle distance between the carbon composite materials can be maintained, and the agglomeration can be reduced. The above dispersion index can be 25 to 65%, or can be 30 to 60%.

[0099] By appropriately adjusting the average particle diameter of the carbon material as the base material, the water-soluble salt concentration, the pH of the solvent, and the conductivity of the solvent, the above dispersion index can be maintained within the above range.

[0100] Specifically, the above dispersion index can be measured by the method described in the examples.

[0101] For the carbon composite material of the present invention, the larger the absolute value of the ζ potential, the greater the electrostatic repulsive force between the carbon composite materials, and the more stable the dispersion. From the viewpoint of further improving the dispersion of the carbon composite material, the absolute value of the ζ potential of the carbon composite material can be 30 to 60 mV, or can be 30 to 55 mV, or can be 30 to 50 mV.

[0102] It should be noted that the above ζ potential can be measured by the method described in the examples.

[0103] In the Raman spectroscopy of the carbon composite material of the present invention, the peak intensity I of the D band in the range of 1300 to 1400 cm -1 and the peak intensity I of the G band in the range of 1550 to 1650 cm D The peak intensity ratio (I -1 / I G ) can be 0.10 to 0.50, or can be 0.11 to 0.40, or can be 0.12 to 0.30. If the above peak intensity ratio (I D / I G ) is within the above range, it means graphene with few defects. D / I G )

[0104] It should be noted that the D band is a peak derived from the defects of the carbon composite material, and the G band is a peak derived from the graphite structure of the carbon composite material.

[0105] [Dispersion liquid]

[0106] The dispersion liquid of the present invention is formed by dispersing the carbon composite material of the present invention in a dispersion medium.

[0107] As the dispersion medium, as long as it is a medium that can disperse the carbon composite material, there is no particular limitation, and it can be a polar solvent. There is no particular limitation for the polar solvent. For example, water, methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol (IPA)), butanol, acetone, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone can be cited. One kind of polar solvent can be used, or two or more kinds can be used in combination. Based on the high affinity with the carbon composite material, any one of water, methanol, ethanol, 1-propanol, 2-propanol, N-methylpyrrolidone, N,N-dimethylformamide, and a mixed solvent of at least two of these can be selected from these. A mixed solvent containing water and alcohol can be selected, or a water / 2-propanol with a mixing ratio (volume ratio) of 50 / 50 to 70 / 30 can be selected.

[0108] In addition, as the non-polar solvent, for example, it can include butyl ethers such as butyl butyrate, butyl propionate, butyl valerate, etc., alkane solvents such as hexane, cyclohexane, heptane, cycloheptane, octane, cyclooctane, etc., and carboxylic acid esters.

[0109] From the viewpoints of the dissociation of the anionic functional group and the dissociation of the counter cation of the anionic functional group, the pH of the dispersion medium at 25°C can be 4.8 to 10.0, or 4.9 to 9.5, or 5.0 to 9.0. If the pH of the dispersion medium is 4.8 or more, the dissociation of the anionic functional group is promoted, and if it is 10.0 or less, the dissociation of the counter cation of the anionic functional group is promoted.

[0110] The above pH can be measured using a pH meter (for example, manufactured by Horiba, Ltd., model: LAQUA D-210P, 25°C), etc.

[0111] From the viewpoint of the electrostatic repulsive force acting on the dispersed particles, the conductivity of the dispersion medium at 25°C can be 70.0 μS / cm or less, or 0.1 to 50.0 μS / cm, or 0.2 to 20.0 μS / cm, or 0.3 to 10.0 μS / cm.

[0112] The above conductivity can be measured using a conductivity meter (e.g., manufactured by EUTECH, model: PC450), etc.

[0113] For the pH and conductivity of the dispersion medium at 25 °C, by appropriately adding inorganic acids such as sulfuric acid and hydrochloric acid; organic acids such as acetic acid and citric acid; hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; and ammonia, etc., it can be adjusted to the above ranges respectively.

[0114] (Other components)

[0115] The dispersion of the present invention may also contain other components. As other components, there is no particular limitation, and it may contain nano-fillers; and additives such as thickeners, viscosity modifiers, resins, curing agents, flame retardants, surfactants, defoamers, ultraviolet absorbers, etc.

[0116] For the dispersion, carbon composite materials and additives added as needed can be added to the dispersion medium, and it can be prepared by thoroughly stirring manually or with a stirrer.

[0117] Regarding the solid content concentration of the dispersion of the present invention, based on the total amount (100% by mass) of the dispersion, it can be 0.1 - 35.0% by mass, or 1.0 - 30.0% by mass, or 3.0 - 20.0% by mass. If the solid content concentration is 0.1% by mass or more, characteristics can be imparted by the dispersed carbon composite materials, and if it is 35.0% by mass or less, it can be easily redispersed.

[0118] It should be noted that in the present invention, the "solid content concentration" refers to the content (concentration) of components other than the dispersion medium.

[0119] In addition, from the viewpoint of achieving high dispersibility and long-term dispersibility, the content of the carbon composite material in the solid components can be 0.1 - 25.0% by mass, or 0.5 - 20.0% by mass, or 1.0 - 15.0% by mass.

[0120] (Use)

[0121] As the uses of the carbon composite material of the present invention, electronic components such as conductive composites and electrodes can be cited; building materials; coating materials; medical devices; and heat-releasing materials, etc.

[0122] Examples

[0123] Next, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples at all.

[0124] (Example 1)

[0125] At room temperature (25 °C), in a nitrogen environment, 2.0 g of natural graphite (manufactured by Nippon Graphite Industry Co., Ltd., ACB-50, average particle size 350 μm), which is the base material of the carbon composite material, and 4.0 g of tripotassium citrate as a water-soluble salt were mixed. Using a ball mill (manufactured by Fritsch, model: P-6, ball diameter 20 mm (material: zirconia)), the rotation speed was set to 600 rpm and the mixing time was set to 55 minutes, and mixing and stirring were performed (mixing condition 1). Then, after washing with ion-exchanged water, filtration was carried out, and drying was performed at 60 °C to obtain a carbon composite material.

[0126] 0.3 g of the obtained carbon composite material was added to 100 mL of a mixed solvent of ion-exchanged water and 2-propanol (IPA) (volume ratio: 60 / 40), and ultrasonic treatment was performed for 3 minutes using an ultrasonic homogenizer (manufactured by SMT Co., Ltd., model: UH-600S) with a chip size of 26 mmφ to obtain a dispersion. For 100 mL of the obtained dispersion, 50 mL was collected each time using a pipette and transferred to two centrifuge tubes. Using a centrifuge (manufactured by Hitachi Koki Co., Ltd., model: CR21N), centrifugation was performed at a temperature of 25 °C and a rotation speed of 1000 rpm for 10 minutes, and the supernatant after centrifugation was sprayed onto a mica plate to prepare a measurement sample.

[0127] The thickness of the obtained measurement sample was measured using an atomic force microscope (manufactured by Hitachi High-Technologies Corporation, model: AFM5300E). As a result, it was confirmed that the thickness was 0.99 nm, which corresponded to 3 layers or less of graphene layers, and the carbon composite material was exfoliated into graphene.

[0128] (Example 2)

[0129] In Example 1, except that the rotation speed of the ball mill was set to 540 rpm and the mixing time was set to 40 minutes (mixing condition 2), the measurement sample of Example 2 was prepared in the same manner as in Example 1.

[0130] (Example 3)

[0131] In Example 1, except that the rotation speed of the ball mill was set to 580 rpm and the mixing time was set to 10 minutes (mixing condition 3), the measurement sample of Example 3 was prepared in the same manner as in Example 1.

[0132] (Example 4)

[0133] In Example 1, except that the rotation speed of the ball mill was set to 280 rpm and the mixing time was set to 75 minutes (mixing condition 4), the measurement sample of Example 4 was prepared in the same manner as in Example 1.

[0134] (Comparative Example 1)

[0135] In Comparative Example 1, the measurement sample was prepared in the same manner as in Example 2, except that tripotassium citrate was not mixed and ion-exchanged water was not used for washing.

[0136] (Comparative Example 2)

[0137] Graphene nanoplatelets (also known as carbon composite materials) (manufactured by XG sciense Co., Ltd., trade name: R10, particle size D(50): 16 μm, number of layers 20) were used.

[0138] (Comparative Example 3)

[0139] In Comparative Example 3, the measurement sample was prepared in the same manner as in Example 1, except that the rotation speed of the ball mill was set to 500 rpm and the mixing time was set to 20 minutes (mixing condition 5).

[0140] (Comparative Example 4)

[0141] Graphene oxide (also known as carbon composite material) (manufactured by NSC Co., Ltd., particle size D(50): 3.6 μm) was used.

[0142] [Evaluation]

[0143] The following evaluations were performed on the carbon composite materials (measurement samples) obtained in Examples 1 to 4, the graphene nanoplatelets in Comparative Example 2, and the graphene oxide in Comparative Example 4. The results are shown in Table 1.

[0144] (1) Particle size (D50), particles with a particle size of 50.0 μm or more (volume%)

[0145] 0.02 g of the measurement powder was added to an aqueous solution of sodium hexametaphosphate at 500 mass ppm, and ultrasonic treatment was performed for 6 minutes using an ultrasonic homogenizer (manufactured by SMT Co., Ltd., UH-150) with a chip size of 26 mmφ to prepare a dispersion with a solid component concentration of 0.2 g / L. For the obtained dispersion, the particle size (D50) at which the cumulative number from the small particle side was 50% was measured using a laser diffraction particle size distribution analyzer (manufactured by MicrotracBEL Corp., MT3300EXII), and the occupancy ratio (volume%) of particles with a particle size of 48.0 μm or more was measured. The particle refractive index (Particle Refractive Index) was 2.66 in all measurements.

[0146] (2) Specific surface area

[0147] According to the flowing nitrogen adsorption BET single-point method of JIS R 1626-1996, 50 mg of the powder was collected for measurement. To reduce the influence of organic substances, after heating at 250 °C for 15 minutes, the specific surface area was measured using a BET measuring machine (manufactured by MOUNTECH Co., Ltd., Macsorb HM model-1220).

[0148] (3) Cation concentration

[0149] 0.1 g of the measured powder was placed in a platinum crucible for ashing, and then dissolved using boric acid and sodium carbonate and dissolved in a hydrochloric acid solution. It was made up to 200 mL with ultrapure water, and quantitative analysis of the target cations was carried out using an ICP emission spectroscopic analyzer (manufactured by analytik-jena AG, model: PQ9000 / Elite).

[0150] (4) Detection of trace cation components

[0151] 0.1 g of the measured powder was fixed on the measuring stage of an electron microprobe analyzer (manufactured by JEOL Ltd., model: JXA-8539F). Under the conditions of an acceleration voltage of 15 kV, a probe current of 1.0×10 -7 A and an analysis area of φ100 μm, a trace analysis measurement was carried out for 1000 ms to determine whether cation elements could be detected, and evaluation was carried out according to the following evaluation criteria.

[0152] [Evaluation criteria]

[0153] 〇: Cation elements were detected at 20 ppm or more.

[0154] ×: Cation elements were not detected because they were less than 20 ppm.

[0155] (5) Cation modification rate

[0156] The cation modification rate is defined as the cation concentration per unit specific surface area.

[0157] Cation modification rate (mass ppm / (m 2 / g)) = Cation concentration (mass ppm) / Specific surface area (m 2 / g) (1)

[0158] (6) Calculation method of dispersibility index

[0159] 0.3 g of the test powder was added to 100 mL of a mixed solvent of ion-exchanged water and IPA (volume ratio: 60 / 40), and ultrasonic treatment was performed for 3 minutes using an ultrasonic homogenizer with a chip size of 26 mm φ (manufactured by SMT Co., Ltd., UH-600S) to prepare a dispersion with a solid component concentration of 3 g / L. 100 mL of the obtained dispersion was collected 50 mL at a time using a pipette and transferred to two centrifuge tubes. Centrifugation was performed at a temperature of 25 °C and a rotational speed of 1000 rpm for 10 minutes using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR21N). The supernatant after centrifugation was aspirated using a pipette and placed in a 0.1 mm cuvette, and the absorbance was measured at a fixed wavelength of 660 nm using a spectrophotometer (manufactured by JASCO Corporation, V-730). The dispersibility index was calculated using the following formulas (3) and (4). Among them, the absorbance coefficient was set to 3200 (L / g·m), the cuvette thickness was set to 0.0001 (m), and the initial concentration was set to 3 (g / L).

[0160] Supernatant concentration [g / L] = (Absorbance) / (Absorbance coefficient × Cuvette thickness) (3)

[0161] Dispersion index (X) [%] = [(Supernatant concentration) / (Initial concentration)] × 100 (4)

[0162] The dispersibility was evaluated according to the following evaluation criteria.

[0163] [Evaluation criteria]

[0164] A: The dispersion index is 50% or more and 70% or less.

[0165] B: The dispersion index is 18% or more and less than 50%.

[0166] C: The dispersion index is less than 18%.

[0167] (7) Raman spectrum peak intensity ratio (I D / I G )

[0168] To 100 mL of a mixed solvent of ion-exchanged water and IPA (volume ratio: 60 / 40), 0.3 g of the measurement powder was added, and ultrasonic treatment was performed for 3 minutes using an ultrasonic homogenizer with a chip size of 26 mmφ (manufactured by SMT Co., Ltd., UH-600S) to obtain a dispersion with a solid component concentration of 3 g / L. 50 mL of the obtained dispersion was collected each time using a pipette and transferred to two centrifuge tubes. Using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR21N), centrifugation was performed at a temperature of 25°C and a rotational speed of 1000 rpm for 10 minutes. The centrifuged dispersion was dropped into a membrane filter with a pore size of 5 μm, and suction filtration was performed. Then, Raman spectroscopy measurement was performed on the sample on the membrane filter using a laser Raman spectroscope (manufactured by Horiba, Ltd., HR-800). The measurement conditions were set as a laser wavelength of 514.79 nm and a measurement wave number of 100 - 4000 cm -1 .

[0169] Using the peak intensity I of the D band in the obtained spectroscopic spectrum in the range of 1300 - 1400 cm -1 and the peak intensity I of the G band in the range of 1550 - 1650 cm D , the peak intensity ratio (I -1 / I G ) was calculated. D / I G ).

[0170] (8) ζ potential

[0171] To 100 mL of a mixed solvent of ion-exchanged water and IPA (volume ratio: 60 / 40), 0.3 g of the measurement powder was added, and ultrasonic treatment was performed for 3 minutes using an ultrasonic homogenizer with a chip size of 26 mmφ (manufactured by SMT Co., Ltd., UH-600S) to obtain a dispersion with a solid component concentration of 3 g / L. 50 mL of the obtained dispersion was collected each time using a pipette and transferred to two centrifuge tubes. Using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR21N), centrifugation was performed at a temperature of 25°C and a rotational speed of 1000 rpm for 10 minutes. The supernatant after centrifugation was diluted 10-fold with ion-exchanged water, and the ζ potential of the obtained diluted solution was determined by electrophoresis light scattering method using a ζ potential measurement system (manufactured by Otsuka Electronics Co., Ltd., ELSZ-1000ZS).

[0172] The dispersibility was evaluated according to the following evaluation criteria.

[0173] [Evaluation criteria]

[0174] A: The absolute value of the ζ potential is 40 mV or more and 60 mV or less.

[0175] B: The absolute value of the ζ potential is 30 mV or more and less than 40 mV.

[0176] C: The absolute value of the ζ potential is less than 30 mV.

[0177] (9) Oxygen content

[0178] Fix 0.1 g of the measured powder on the measurement stage of an electron microprobe analyzer (manufactured by JEOL Ltd., model: JXA - 8539F), and measure the oxygen content under the conditions of an acceleration voltage of 15 kV, a probe current of 1.0×10 -7 A and an analysis area of φ100 μm.

[0179] (10) Weight loss rate

[0180] Using a TG - DTA measuring device (manufactured by Bruker AXSS Ltd., model: 2000SR), measure the weight loss rate of approximately 3 mg of the measured powder (standard substance: Al2O3, standard substance amount: 15.5 mg) under the conditions of a nitrogen environment (air volume 150 mL / minute) and a measurement temperature (room temperature to 1000 °C, heating rate 10 °C / minute), and evaluate the heat resistance according to the following evaluation criteria for heat resistance indexes.

[0181] Calculate the weight loss rate using the following formula (5).

[0182] Weight loss rate (%) = {[mass before measurement (mg) - mass after measurement (mg)] / mass before measurement (mg)} × 100 (5)

[0183] [Evaluation criteria]

[0184] Heat resistance index A: The weight loss rate is 0 or more and less than 1.1%.

[0185] Heat resistance index B: The weight loss rate is 1.1% or more and less than 2.1%.

[0186] Heat resistance index C: The weight loss rate is 2.1% or more.

[0187]

[0188] As can be seen from Table 1, compared with the carbon composites of Comparative Examples 1 to 3, the carbon composites of Examples 1 to 4 have good dispersibility when made into a dispersion liquid and are difficult to re-aggregate. Each of the particle size (D50), the occupancy ratio of particles with a particle size of 50.0 μm or more, and the cation modification rate of the carbon composites of Examples 1 to 4 all meet the specific regulations of the present invention, while the carbon composites of Comparative Examples 1 to 3 do not meet at least one of these regulations. In addition, it can be seen that compared with Comparative Examples 2 and 4, Examples 1 to 4 have a lower oxygen content rate, so the weight reduction rate is lower and the heat resistance is better. As a result, it can be seen that Examples 1 to 4 simultaneously satisfy dispersibility and heat resistance.

Claims

1. A carbon composite material, which is a carbon composite material formed by introducing a modifying group into a carbon material. Among them, in the volume-based particle size cumulative distribution measured by the laser diffraction scattering method for the carbon composite material, the particle size D50 of the cumulative 50% from the small particle side is 0.5 to 15.0 μm, the occupancy ratio of particles with a particle size of 50.0 μm or more is 30.0% by volume or less, the cation modification rate of the carbon composite material calculated by the following formula (1) is 1.0 to 50.0, and the modifying group contains an anionic functional group and a counter cation of the anionic functional group. Cation modification rate = cation concentration / specific surface area (1) The unit of the cation modification rate is mass ppm / (m 2 / g), the unit of the cation concentration is mass ppm, and the unit of the specific surface area is m 2 / g.

2. The carbon composite material according to claim 1, wherein the anionic functional group includes at least one or more selected from the group consisting of a carboxyl group, a carbonate group, a sulfonic acid group, and a phosphoric acid group.

3. The carbon composite material according to claim 1 or 2, wherein the counter cation includes at least one or more selected from the group consisting of a potassium ion, a sodium ion, a lithium ion, a barium ion, a calcium ion, a magnesium ion, a rubidium ion, and an ammonium ion.

4. The carbon composite material according to any one of claims 1 to 3, wherein the concentration of the counter cation contained in the carbon composite material is 50 to 5000 mass ppm.

5. The carbon composite material according to any one of claims 1 to 4, wherein the oxygen content rate contained in the carbon composite material is 0.01 to 2.00 mass%.

6. The carbon composite material according to any one of claims 1 to 5, wherein the carbon material of the base material of the carbon composite material includes at least one or more selected from the group consisting of graphite, natural graphite, artificial graphite, flake graphite, expanded graphite, pyrolytic graphite, graphene, and carbon nanotubes.

7. A dispersion liquid, wherein the dispersion liquid is a dispersion liquid in which the carbon composite material according to any one of claims 1 to 6 is dispersed in a dispersion medium.

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